Radio beacon



P 1952 P. B. TAYLOR 2,609,534

RADIO BEACON Filed Aug. 24, 1944 REFERENCE CARRIER CHANNEL 6 j R-F Q PH SER POWER MASTER 0 l5 KEYED SIDE-BAND CHAN NEIL is BAL' RECEIVER D POWER 24 WITH MO MP. l AVC '8 2o GAINCO TPOL TONE 2| G EN. 3's 2 FIGJ V" 2 REFERENCE CARRIER CHANNEL y osc. R-F v XMITTER Y Fl \50 F|G.3 j FIG 4 osc. BAL. Y R-F XMITTER F2 MOD"? AMP, I F2 ,L

52 T 54 N T 62 as Tom CODER 4 GEN. N f 5 s KEYEDSlDE-BAND CHANNEL I I AMP. DETECTOR RETE EQE I BROADLY XMITTER i I I D RECTIONAL T f HGS V SIGNAL AVG INDJCATO KEYED I l SIGNAL SHARPLY XMITTER HI DIRECTIONAL FIG. 6

I I INVENTOR. To I PAUL B.TAYLOR Patented Sept. 2, 1952 UNITED STATES PATENT] ge RADIO BEACON Paul B. Taylor, Dayton, Ohio Application August 24, 1944, Serial No. 551,050

13 Claims. (01. 343-106) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757)- The invention described herein may be manufactured and used by or for the Government for governmental purposes, without th payment to me of any royalty thereon.

This invention relates to improvements in radio signaling, particularly for the purpose of providing improved omnidirectional radio ranges or beacons.

In one prior system of this type, a sharp unldirectional beam of radio energy is rotated in azimuth at a relatively slow rate, say one revolution every two minutes. As said beam is rotated, it is modulated with a series of identifying code letters, a different letter being used for each of a plurality of directions. As the beam sweeps through a sector of space in which there is located an ordinary nondirectional receiver, the operator of such receiver will hear a series of successive code letters which vary in strength, the code letter received with maximum strength indicating to him the direction of origin of the received signal. Systems of this type permit the use of an ordinary communication receiver for direction determination, a factorwhich is of importance where space is at a premium and the amount of equipment utilized musttherefore be kept at a minimum; as is the case with airborne equipment.

The above system is, however, subject to several limitations resulting from various factors at the point of reception, which cause a decrease in the accuracy of direction determination. For instance, if the receiver is equipped with automatic volume control (AVC) or is of the type which inherently provides limiter action, such as a super-regenerative receiver, the gradations in volume of the code signals heard will be more or less evened out, thereby'reducing the accuracy of azimuth determination. Moreover, if the receiver is located on a rapidly moving craft such as an airplane, large changes in distance from the transmitter will occur before the beam thereof has swept through the sector involved, thus producing changes in field intensity of the received signals which bear no relation to the beam direction. Furthermore, if the antenna, of such craft is not perfectly omnidirectional, changes in attitude of the craft, i. e., its orientation with respect to the direction of the signal origin, will also affect the received signal strength, so that the signal intensity mayjvary rapidly while the plane is changing its heading. It is a principal object of this invention to provide animproved directional signaling system in which the above-mentioned difficulties are largely reduced or eliminated; It is a further object of the invention to' provide an improved system of this type in which the intensity of the direction-indicating signal depends 1 predominantly on the direction of the beamed signal and is largely independent of local factors afiecting the intensity of saidsignal at the point of reception. Yet another object of the invention is to provide an improved omnidirectional radio range whichwill give accurate direction indication with a receiver having inherent limiting ac;- tion or equipped with AVC. "1

Toward the attainment of these and other objects, the radio range signal is made up of-at least two components'having difierent frequency and directional characteristics. The intensity of the signal in the output of the receiver is made dependent upon the ratio of the amplitudesof both components at the receiver input." By providing the receiver with AVC,said'output;in

tensity is kept substantially independentof like, variations in amplitudes of both components at the receiver input.

In accordance with a preferred embodiment of the invention, one component of the'signal is' an unmodulated carrier, transmitted over an antenna having a nondirectional or broadly-directional lobe pattern. The other component isa tonemodulated side-band signal, with suppressed carrier, transmitted over a continuouslyfrotating antenna having a relatively sharp, preferably unidirectional lobe pattern. Th side-band component is also keyed as the antenna is rotated to provide code signals indicative of the instantaneous direction of the axis of the lobe. As the lobe of the directional component sweeps through a receiver location, the modulation depth, and hence the intensity of the signal in the receiver output will be maximum when said axis points directly at the receiver.

lt is well known in the art that in a system inwhich' car-'" rier is added to side bands the maximum dept h other directions it may taper oil, but still must be kept large compared to the amplitude of the signal of sharp directivity in that direction.

In accordance with another embodiment of the invention, two carriers of different frequencies are generated. One is umnodulated and nondirectionally transmitted, while the. other is sup--v p -game -ime el ie in the same manner as described above, and its side bands are close enough in frequency to be received in the same receiver, but far enough apart that the beats between the received carrier and side-bands are,

of sueh high frequency as to be either superaudible or substantially attenuated by the audio channels or the receiver. Only the beats between the side-band frequencies'will be heard,

In accordance with still another embodiment of the invention, two carriers or difiere nt ire; quencies are separately transmitted. One is continuously and nondirectionally transmitted; he oth r s ir ona re sm tt d an e e I lose ,6 ough' in i quency' 't'o.

' estate/ he e embed me tst e refere ce flimsy ale b ene i d ver earn which isrotated in tlor'ial beajfn, the

For a be ter u der ta dingit th n en o ifet i f e dfuf f f b i e e e o size towns e ewi g s i t l t; s

fa dit Fig. 2 is a block diagram of a receiveresuitable 1.1 18- A W I U 06k iegtem o tw ur.-

flea ni hesvteml a 5-1- an F i sued; diagram of aportion oliFig. 2,

"i "que e q w en is adiat d y dizflect nal antenna 16. The side-band cha nel m ie i s a qarr' e p re s' e e a e 'fm i later; I8; and a tuneu asnjpowe iampnfie it",

the. outi ut'bi w ic radiated 'byiai'hi'e'hiy; d1:

anger mo e 3 1 1 ent nnazliin l P l s zzle ide' efle w lfi fien i the n e lobfef unidirectional, Reflector; 2 6 'ina'y 1 be para! bolic if a"'sir'igle dipol'ejlsused, orffitjr'nafbe fiatlii a dipole arrayis used; The usual 'g aincontrol means l5 and 2| are provided for vary? the Power t i ef mp ies as r s e tively,

Antenna; 22'. isfcontinuouslyrotated inlazimuth te eie c vx i ee ew. FQWQFFWWi get ins cod al he rmer s connection with the accompanying es wiil eean d t im and d aws, afconventional Ave; circuit which. is

- R,-F- amplifier 20'and radiated by directional rotates, in synchronism with the antenna, a coder 30, comprising a disc 32 having camrning teeth 34 cut around its entire periphery to form predetermined code letters. For each direction that the antenna lobe points to, a separate code letter is used to identify to a listener the instananeou d r ction of a d, ntenna 0 mingite'eth 3 4 serve tolconlti ol aflgey ing switch 38 which couples the output of an audio-frequency tone generator 38 to the balanced modulator [8 to modulate the carrier and produce modulation side-bands which are amplified by antenna 22'. 5 The speed of rotation of the directional-antenna is usually much lower than the frequency of the tone generator 33, said speed beiri'g' unrelated to the modulation components a of the transmitted; wave.

' wtb'wh bthe's' are applied. Theo am Substant a con tant he a? Thu S the I'e iS provided a radio-range transmitter in which antenna 1'6 transmits a nondirec- 1 tional reference signal component. in t e or 1 unmfld i et 33 m 6. 43 '2 trans: s; 1 61 9 a Shar ,y definedvdir etihya seco d signal" componenfin, the'form of key d si e-ff bands of. the tone mod lation, with, carrier m se y" mime 5 m ies es eem. Y 22'; the azimu h. Qf aid, sectorisrotated the same time coder 30 will code-modulate themed: ulation side-band component that, distinctive e-signal a e e e i o dfthe m 3 Q which is indicative'di a, given direction ree -l mission; To determine "at a. second point the dir t n f hel ervir'eb'i er 5 antenna 42," is use iflFigfi. 6, such ax aebei eean'y shwa Giver meriee i mp fier,

' eQ -eu nt o tial wh sk s deteimii ei y V h -ave a e m l i ee'ei the Waveel he ame fier output. This .potentialis applied; to the g of f f moreldt' e emnliflertubestema between the carrier andside-ba'rid components,- i. e., the depth of modulation, and'hencethe loudness of the received signals, On theyother hand, other conditions which willtend to vary the strength of both signal components will result in activation of the AVG circuit by the carrier component so thatsaid variation will be compensated for.

Itis important that the two components at the receiver have the proper amplitude and phase relation to yield an amplitude modulated si nal. For this purpose, therelative amplitudes of the signals in both transmitter channels should :be properly adjusted bythe gain controls 15 and 2|. Phaser l2 should also be adjusted to properly phase the carrier signal with respect to the sideadjustment can be provided for in both channels.

Fig. 3 shows another embodiment of the invention, in which the nondirectional reference component and the beamed component are of the different frequencies Fl and F2 generated by separate oscillators 50 and 52, respectively. The output of oscillator52 is modulated by the tone generator 56 in a balanced modulator 54, which suppresses the carrier and yields only the modulation side-bands. In other respects this system is similar to that in Fig. 1. The frequencies Fl and F2 are sufficiently close to be received by the same receiver, but far enough apart that the beats between the carrier component FI and the side-bands of the suppressed carrier component F2 in the receiver are so high as toibe either superaudible or too high to be effectively transmitted by the audio circuits of the receiver. The side-band frequencies will, however, beat with each other to yield an audible signal which may be interpreted in that same manner as above described in connection with Fig. 1. The embodiment in Fig. 3 does not, however, need any adjustment in phase relation between the two signal components, and hence there. is no need for a phaser such as I2 in Fig. 1. As in the first embodiment, the unmodulated reference component, provided by oscillator Fl, controls the AVG action at the receiver, while the effective direction of the side-band component, provided by oscillator F2, controls the intensity of the receiver output to indicate the direction of signal transmission. In order to prevent apparent broadening of the beam by the AVG action of the receiver, the amplitude of the reference component should be greater than the sum of maximum amplitudes of the side-bands in the beamed component. a

Fig. 4 illustrates a thirdembodiment of the invention, in which the two signal components are provided by two transmitters 60 and 62 operating at different frequencies Fl and F2. The output of transmitter 60 is unmodulated and radiated by a nondirectional antenna 64. The output of transmitter 62 is transmitted by the rotating directional antenna 66. No tone modulation is provided for the beamed component in this system, as is the case with the first two embodiments. The coder 68, which is rotated in synchronism with antenna 66, merely keys transmitter on and off in accordance with the various code signals. Frequencies FI and F2 are close enough to provide an audio beat signal in the output of the receiver when both components are received, the intensity of said audio signal providing the indication of the direction of the transmitted signal. The timeconstant of the AVG circuit of the receiver used'with this system should preferably be slow enough to avoid any substantial removal of the'code modulations but fast enough to compensate fonrapid changes'in field intensity due to the aforementioned local factors. .In order to minimize apparent broadening of the beam due to AVC action, the amplitude of the nondirectional component should be larger than that of the beamed component.

All the above described embodiments can be modified in a manner shown in Fig. 5. Instead-of nondirectionally transmitting the reference component, the latter is also transmitted over a di rectional antenna 10 which is rotated in unison with the sharply; directional antenna 12 which carries the keyed .signal'component. Both antennashave their lobes pointing in the same direction. Antenna has, however, a directional fiatenosed lobe pattern which is considerably broader thanthat of said sharply-directional antenna 12, and of such extent that it is wide enough to cover the minor lobe sectors of antenna 12. This expedient permits a substantial saving in the power of the reference carrier component of the signal.

In all the above embodiments the nondirectional or broadly directional channel can be used to send a station-identifying signal and for telegraphic or telephonic communication purposes. Well known electrical methods involving stationary antennas can be used for rotating the beam in place of the mechanical methods described. It will be obvious that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the app nded claims.

I claim:

1. A directional radio system comprising radio transmitting means and radio receiving means; said transmitting means comprising first and second antennas situated at substantially the same point, the second antenna being more sharply directional than the first, means for transmitting from said first antenna a wave without any modulation thereon, and means for transmitting from said second antenna a suppressed-carrier, amplitude-modulated wave; said radio receiving means comprising a relatively non-directional means for receiving and combining the wave radiated from both of said anten- 112.8 to produce a resultant amplitude-modulated signal, an amplifying circuit upon which said resultant signal is impressed for amplifying said resultant signal, an automatic volume control circuit energized by the output of said amplifying circuit for controlling the gain thereof, said automatic volume control being predominantly responsive to the average amplitude of said resultant signal, and signal indicator means coupled to the output of said amplifying circuit.

2. A system as set forth in claim 1, wherein said first antenna is non-directional and said second antenna is unidirectional, means for continuously rotating the effective direction of said second antenna, and means for varying the amplitude modulation characteristic of the wave transmitted from said second antenna in synchronism with said rotation to provide a distinctive modulation for each effective direction.

3. A directional radio system comprising radio transmitting means and radio receiving means; said transmitting means comprising first and second antennas situated at substantially the same point, said second antenna being more ing means for receivingandcombiningthe waves radiated fromboth' of a said antennas toproduce a resultant amplitude-modulated wave, an amplifying means upon which-said resultant is i-m-- v pressed for amplifying said resultant wave, an automatic volume -con trol circuit energized by the output of said amplitying -meansfor control ling the gain thereot, said-automaticvolume 0on trol circuit fleeing predominantly responsive the average amplitude of said resultant wave; and signal indicator means coupled to the output of-saidampilifyingmeans-j 4. A system as set forth in -claim '3', wherein said first; antenna is substantially non-direc t-ional. V

5. A system as set forth in. claim 4-,: wherein said second antenna is unidirectional' 6. A system asset forth n; claim 5, including means forcontinuously; rotating the effective direction of said second antenna andsynchronously varying the modulation of said second wave to-provide adistinctive-modulation for effective direction. 5 r

7 A system as-fset for th'in claim Xi, wherein both of said wavesareotthe same frequency-and cophasally-transmitttd.

8. A system as set forth in claim 6, wherein said waves are of different frequency; 7

9. A directional radio system comprising radio transmitting means and radio receivingmeans;

said transmitting means comprising a fixed-frequency undamped wave source, a pair-- ofchannels coupled in parallel= to said source, a-substantially' non d-irectional antenna in one -o f-said' channels for radiating said wave withoutany modulation thereon, asource of-audio-frequency signal, a balaneedmodulator in the o't-herof 'said channels for modulating said wave with said signal while suppressing saidcarrier, a unidirectional antenna the other of said channels forradiating thesuppressed-carrier waves; means;

for continuously rotating said antenna and synchronously interrupting said audio-frequency signal to provide a distinctive code modulation.

for each distinct direction, both antennas being situated at substantially the-same point-, and

means in at leastone of said channels: to sci-ad;- just the amplitude and phase relationofsaid waves that when both'waves are combined-they produce an amplitude-modulated wave; said radio receiving means-comprising a relatively non-directional means for're'ceiving'and combin ing the waves radiated from both of said anten nets to produce aresul-tant amplitude-modulated signal, anamplifyingchannel upon which said resultant signal is impressed for amplifying said resultant signal, an automatic-lvolume control circuit energized by the output of said amplifying channelfor-control-l ing the gain thereof, said automatic volume control circuit being predomi-f n'antly responsive to the average; amplitude of said resultant signal, 'and signal indieator means coupled to the output of said amplifier means. ll). system for radiating a modulated signal which when received produces a signal 'having a 'means for synchronously varyingxa modulation characteristic of, said modulated wave with each. change ineffective direction. 7

IL. A system as setforth in claim 1-0,v wherein said waves are of the same frequency.

. 12., A system as set forth in claim 11, wherein both. waves are eophasally radiated.-

REFERENCE$ CITED- The following references are of record-inthe file of this patent:

UNITED STATES; PATENTS 

